Method and device for generating a passive movement in a diagnostic device

ABSTRACT

A method and an apparatus for generating a passive movement of a patient in a magnetic resonance tomograph. The apparatus includes a support for supporting at least one body part of the patient. The support, together with a patient bed can be moved into a passage of the magnetic resonance tomograph. Driven by a motor, the support can be swiveled about at least one axis inside the passage of the magnetic resonance tomograph. The components of the support and its drive, which are disposed inside the passage of the magnetic resonance tomograph, are made of non-ferromagnetic materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of a priority under 35 USC 119(a)-(e) and (g) to German Patent Application No. 102 14 798.1 filed Apr.1, 2002 and German Patent Application No. 202 05 012.2 filed Apr. 1,2002 and German Patent Application No. 102 35 963.6 filed Aug. 6, 2002,the entire contents of each which are hereby incorporated by reference.This application claims the benefit of an earlier filing date in theUnited States under 35 USC 120 or 121 or 363 or 363(c) to U.S. patentapplication Ser. No. 10/375,717 filed Feb. 27, 2003 the entire contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates to a method and apparatus for generatinga passive movement of a patient in a magnetic resonance tomograph with asupport for supporting at least one body part of the patient, whichsupport together with a patient bed or the like can be moved into animaging passage of the magnetic resonance tomograph.

2. The Prior Art

To provide for an optimum diagnosis of injuries and disorders of joint,such as an ankle joint it is known to scan a patient of at leastrelevant body parts by means of a magnetic resonance tomograph (MRT) andto make a diagnosis on the basis of the images obtained. For thispurpose, it is frequently required to position or to be able to move thebody part concerned in different and defined ways as required.Therefore, apart from static instantaneous images, static images have sofar been produced in various joint positions. The joint positions areadjusted manually via a mechanism, and viewing the resulting images iseffected by means of an image loop (cine-mode). However, this isparticularly time-consuming and therefore can only be applied inindividual cases. Thus the possibilities of a modern magnetic resonancetomograph, which also provides for very fast image recordings, are notutilized. Hence, the diagnostics frequently indispensable with amagnetic resonance tomograph, which can excellently represent both theosseous and the cartilaginous parts of the human body as well as itssoft-tissue structures, is not being used optimally.

In addition, there is the disadvantage that despite this presently mostmodern form of diagnosis not all disorders or injuries and damage to thehuman body can be detected by static instantaneous images, in particularas it has not been possible so far to make images in movement of asufficient quality. However, this impairs the clinical diagnostics, asthus the probability (sensitivity) to diagnose existing pathologicalfindings with diverse structures is not yet optimally possible or partlynot possible. In magnetic resonance tomograph, in contrast to X-raydiagnostics, there have so far not been any firmly predefined andreproducible settings to provide for the representation of real-timemovements.

This in particular due to the fact that as a result of the strongmagnetic field in a magnetic resonance tomography, the use ofconventional movement apparatuses is not possible. Conventionalelectromechanical motors, which are usually employed in movementapparatuses, consist of magnets and coils which in the strong magneticfields of (0.2-3 Tesla) of a magnetic resonance tomograph deflectparticularly strongly and thus lead to image distortions, so-calledimage artefacts. Once such image artefacts occur, however, a properdiagnosis no longer is possible.

BRIEF DESCRIPTION OF THE INVENTION

Therefore, an embodiment of the invention provides a method and anapparatus for a defined reproducible passive movement of a patient in amagnetic resonance tomography without producing image distortions, i.e.,image artifacts, which make a diagnosis impossible.

An embodiment of the invention, provides that driven by a motor, thesupport can be swiveled about at least one axis inside the imagingpassage of the magnetic resonance tomograph, and that the components ofthe support and its drive, which are disposed inside the imaging passageof the magnetic resonance tomograph, are made of non-ferromagneticmaterials. Due to this structure, the sensitivity of the magneticresonance diagnostics with respect to the examination of the joints isincreased distinctly. Thus predefined continuous movements can be setand the movements can be reproduced, in order to be able to representreal-time images (online images). The method and apparatus allows a bodypart to move in the magnetic resonance tomograph within the full scopeof movement, passively and as desired for the respective diagnosticsituation. Since the diagnostic possibilities have thus been improvedand expanded, suspected injuries and the like can be detected andverified far better than has so far been possible. Since the componentsused in the imaging passage of the magnetic resonance tomography areformed of non-ferromagnetic materials, the occurrence of imageartefacts, which make a diagnosis more difficult, is reduced inaddition.

In an embodiment the occurrence of image artifacts can furthermore beprevented in that the drive for swiveling the support is effected bymeans of a piezoelectric motor.

Preferably, the drive for swiveling the support is controlled by acontrol unit, which is electrically grounded and shielded from magneticradiation. In the method and apparatus, the movements can therefore beadjusted electronically and automatically controlled from outside theroom of the magnetic resonance tomograph in always the same exactlyreproducible positions. The position between the body part to beexamined and the magnetic resonance tomograph can remain unchangedduring the entire diagnostic procedure. At the same time, however, it isfor the first time possible to perform precisely defined movementscontrolled by motors during the imaging procedure. On the one hand, thisallows the magnetic resonance tomograph operator to specifically take acertain image and on the other hand to represent the movement itself inthe sense of a real-time image. Beside the use of a piezoelectric motorfor driving the support, it is also possible to use pneumatic orhydraulic drives for this purpose.

When the control unit is disposed outside the zone around the magneticresonance tomograph, in which the operation of the magnetic flux densityis 0.2 Tesla, the function of the control unit is not impaired by thestrong magnetic field of the magnetic resonance tomography. At the sametime, image artifacts caused by the control unit can be avoided.

The control unit of the support can further be improved in that thecontrol unit is provided with at least one sensor, in particular with anoptical encoder, for detecting the position of the support or of themotors.

To be able to avoid the occurrence of image artefacts, which makediagnosis more difficult, even more effectively, the control unit can beconnected with the drive of the support and possibly with the sensorsvia electrically grounded and shielded lines, which outside the imagingpassage of the magnetic resonance tomograph are provided with ferrites.

In accordance with another embodiment of the invention, the support whendriven by a motor, can independently be swiveled about two axes. Thus,the physiological movements of the body parts to be examined can berepresented even better.

The physiological movement of an ankle joint can be imitatedparticularly well with the apparatus when the support can be swiveledabout a first horizontal axis and a second axis inclined with respect tothe vertical by about 35° in the horizontal plane and by about 18° inthe sagittal plane. This inclination of the second axis corresponds tothe average geometrical axis of the lower ankle joint as determined byVan den Bogard.

The pressure forces acting on the ankle joint, etc., for instance whenrunning, can be imitated during the examination in the magneticresonance tomograph in that there are provided means for fixing the atleast one body part of the patient on the support, and that at leastportions of the support can be moved relative to the fixing means.Preferably, the support can be moved pneumatically or hydraulicallyrelative to the means for fixing the body part. In this way, a stepwisecompression of the body part to be examined can occur, which likewiseleads to a change in the configuration of the individual parts of thebody, which imitate the loads acting for instance when running or thelike.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features of an embodiment of the present invention will becomeapparent from the following detailed description considered inconnection with the accompanying drawings that disclose severalembodiments of the invention. It should be understood, however, that thedrawings are for the purpose of illustration only and not as adefinition of the scope and extant of the invention as disclosed andclaimed.

In the following an embodiment of the invention will be described indetail by means of embodiments and with reference to the attacheddrawings, in which:

FIG. 1 shows a longitudinal section through an imaging passage of amagnetic resonance tomograph with an apparatus arranged on a patientbed;

FIG. 2 shows a sectional view of the apparatus vertical to the sectionalplane of FIG. 1; and

FIG. 3 shows a side view of the apparatus shown in FIG. 2.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

The apparatus represented in the drawings is provided for use in amagnetic resonance tomograph (MRT) for instance with a magnetic fluxdensity between 0.2 and 3.0 Tesla. The magnetic resonance tomograph isindicated in FIG. 1 by an imaging passage 38. In the illustratedembodiment, the apparatus is arranged for examining or imaging the anklejoint. The apparatus has a support 14 for the heel of the foot and asupport 17 for the sole of the foot disposed at an angle. The inner andouter malleoli of the foot are stabilized by side walls 15, whereas thesupport 17 for the sole of the foot is retained on a rear wall 16. InFIG. 1, the foot to be examined is indicated schematically by thereference numeral 19.

As shown in FIGS. 1 and 2, the apparatus is mounted on a patient bed 35by means of a connecting unit 30. Together with the patient bed 35, apatient lying on his or her back can be moved into the image passage 38of the magnetic resonance tomograph, the apparatus being disposed at oneend of the patient bed 35. By means of buckles 18, the foot can bemaintained fixed in the apparatus. The foot not to be examined can beplaced on another support 29 and is not detected in the examination orimaging.

The apparatus disposed on the patient bed 35 furthermore comprises twovertical side walls 1 and a vertical front wall 2 which merges into ahorizontal front wall 3. On the side opposite the vertical front wall 2a vertical rear wall 4 is provided, which is connected with a lowerhorizontal rear wall 5. Parallel, to the side walls 1 another verticalwall 6 extends, which be means of ball bearings 13 is articulated to theside walls 1 so as to be swiveled about a horizontal axis 33. Thevertical walls 6 are connected with each other by a rear wall 11 and aV-shaped bottom wall 12.

In the V-shaped bottom wall 12, two recesses 27 are provided, which canreceive a fastening unit 9. Via an intermediate part 8, the fasteningunit 9 carries another fastening unit 10 with a gearwheel, on whichthere is mounted the support 14 for the heel as well as the rear wall 16with the support 17 of the sole of the foot. The support 14 for the heelas well as the rear wall 16 with the support 17 for the sole of the footcan be rotated relative to the fastening unit 9 via the fastening unit10. Due to the inclination of the V-shaped bottom wall 12 and thecorresponding configuration of the fastening units 9 and 10, the support14 for the heel with the rear wall 16 and the support 17 for the sole ofthe foot can be rotated about an axis 34 inclined with respect to thevertical by about 35° in the horizontal plane and by about 18° in thesagittal plane.

The fastening units 9 and 10 have associated thereto a piezoelectricmotor 22, which carries a gearwheel 7 with conical tip for moving thefastening unit 10 relative to the fastening unit 9. Similarly, apiezoelectric motor 23 is provided at the vertical side wall 1, whichcarries a first gearwheel 24 which via another gearwheel 26, can bebrought into engagement with a gearwheel 26, which is non-rotatablyconnected with side walls 6. Driven by the motor 23, the side walls 6can be thus swiveled relative to the side walls 1.

At the rear wall 16, a pressure valve unit 20 is disposed, by means ofwhich the support 17 for the sole of the foot can be moved relative tothe rear wall 16. There can thus be produced a continuously variablepressure acting on the sole of the foot.

In one of the side walls 1, two optical encoders 21 are positioned,which can detect the position of the side walls 6 relative to the sidewalls 1. Via lines not represented here, the data determined by theencoders 21 can be transferred to an electrobox 28, which in turn isconnected with a control unit 32 via a shielded cable 36. The controlunit 32 also actuates the motors 22 and 23 via shielded cables 37.Outside the imaging passage 38 of the magnetic resonance tomograph,ferrite cores 31 are disposed on the shielded lines 36 and 37. Theconnection of the lines 36 and 37 with the control unit 32 is effectedvia likewise shielded cable connectors 39.

The materials used for the apparatus are not influenced by the magneticfield of the magnetic resonance tomograph. Therefore they produce noimage artefacts that make a diagnosis impossible when non-ferromagneticmaterials are used for the components disposed inside the imagingpassage 38 of the magnetic resonance tomograph. Such non-ferromagneticmaterials include for instance VA4 stainless steel screws and threads,aluminum plates, pins, screws and air-pressure nozzles made of brass,plastic screws, and glass and ceramic ball bearings. The use ofsemifinished products made of polyoxymethylene (POM) is particularlyfavorable, as this plastic material absorbs the radiofrequency field(RF) and therefore generates no disturbing radiation.

The illustrated embodiment of the apparatus for generating a passivemovement is particularly arranged for the examination or imaging ofankle joints. By means of the motors 22 and 23, the support 14 for theheel as well as the support 17 for the sole of the foot, which isconnected with the rear wall 16, can be rotated such that thephysiological movement of the ankle joint is imitated. By moving thesupport 17 for the sole of the foot relative to the rear wall 16 bymeans of the pressure valve unit 20, a weight load of the foot can beimitated in addition. It is thus possible to make both kinematic andstatic images from different positions inside the imaging passage 38 ofthe magnetic resonance tomograph for research and clinical routinediagnosis. As a result, these real-time images of the movementsconsiderably expand the possibilities for using a magnetic resonancetomograph known per se.

Accordingly, while an embodiment of the present invention have beenshown and described, it is to be understood that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention as defined in the appended claims.

1-10. (canceled)
 11. A method of acquiring images of a movement of abody or at least one part of a body of an object to be imaged in animaging passage of an imaging modality comprising: fixing the body orthe at least one part of a body on a support to be disposed in theimaging passage; generating a defined reproducible passive movementabout at least one axis of the body or the at least one part of a bodyor the support by a non-ferromagnetic motorized drive while disposingthe support and the drive and the body or the at least one part of abody within the imaging passage; and acquiring a series of imagescontinuously in real time while and during imaging and while or duringthe passive movement of the body or the at least one part of a body orthe support.
 12. The method according to claim 11 comprising providingshielding against magnetic flux artifacts in the acquired images or theimages as acquired.
 13. The method according to claim 11 comprisingproviding electrical grounding against artifacts in the acquired imagesor the images as acquired.
 14. The method according to claim 11 whereinthe passive movement comprises applying pressure and/or movement and/orswiveling and/or rotating and/or pivoting to the body or the at leastone part of a body or the support.
 15. The method according to claim 14wherein the applied pressure and/or movement and/or swiveling and/orrotating and/or pivoting is selected from the group consisting ofcontinuous, constant, adjustable, step-by-step, variable and acombination thereof.
 16. The method according to claim 11 wherein thepassive movement comprises applying a load on the body or the at leastone part of a body or the support.
 17. The method according to claim 11wherein the passive movement imitates the physiological movement of thebody or the at least one part of a body.
 18. The method according toclaim 11 wherein the images are kinematic or static images of a positionof the body or the at least one part of a body disposed in the imagingpassage.
 19. The method according to claim 11 wherein a predefinedcontinuous movement of the body or the at least one part of a body orthe support is generated or reproduced by the drive.
 20. The methodaccording to claim 11 wherein the body or the at least one part of abody includes a joint of a living object.
 21. The method according toclaim 11 wherein the body or the at least one part of a body is an anklejoint.
 22. The method according to claim 11 wherein the imaging modalityis a magnetic resonance tomograph.
 23. The method according to claim 11wherein object is an anatomical body part having a joint.
 24. The methodaccording to claim 11 wherein the passive movement is applied pressureand/or rotation and/or swiveling and/or movement and/or pivoting to thesupport while the body or the at least one part of the body is at rest.25. The method according to claim 11 wherein the passive movementimitates a physiological movement of the body or the at least one partof the body.
 26. The method of claim 11 wherein the passive movementcomprises applying pressure to the support to move and/or rotate and/orswivel and/or pivot the body or the at least one part of the body. 27.The method according to claim 11 wherein the passive movement comprisesapplying a weight load on the body or the at least one part of a body orthe support.
 28. The method according to claim 11 wherein the passivemovement produces or reproduces stress on the body or the at least onepart a body or the support.
 29. The method of claim 11 wherein the driveis a piezo-electromotor.
 30. The method of claim 26 wherein the appliedpressure and/or movement and/or rotation and/or swiveling and/orpivoting is selected from the group consisting of continuous, constant,adjustable, step-by-step, variable and a combination thereof.
 31. Themethod of claim 11 wherein the passive movement comprises applying aload on the body or the at least one body art by applying pressureand/or moving and/or swiveling and/or pivoting and/or rotating.
 32. Themethod of claim 11 wherein the passive movement imitates the movement ofthe body or the at least one body part of the body.
 33. The method ofclaim 11 wherein the passive movement is about two independent axes. 34.The method of claim 11 wherein the drive provides for applying pressureand/or movement and/or rotation and/or swiveling and/or pivoting thesupport or the body or the at least one part of a body about at leastone axis.
 35. The method of claim 11 wherein the body or the at leastone part of the body is a living object.
 36. The method according toclaim 11 wherein the support or the body or the at least one part of abody can be applied pressure and/or moved and/or rotated and/or swiveledand/or pivoted independently about two axes.
 37. An apparatus forgenerating a passive movement of a body or at least one part of a bodyof an object to be imaged in an imaging passage of an imaging modalitycomprising: a support for positioning the body or the at least one partof a body, which support can be moved into and disposed in an imagingpassage of the imaging passage; a drive motor for providing a definedreproducible passive movement which can be moved into and disposed inthe passage for applying pressure and/or movement and/or swivelingand/or pivoting and/or rotating the body or the at least one part of thebody or the support about at least one axis inside the imaging passage;components of the support and the drive motor are made fromnon-ferromagnetic materials; and a control unit for controlling thedrive motor to produce while and during the defined reproducible passivemovement a series of images continuously in real time while or duringimaging with the imaging modality.
 38. The apparatus according to claim37 wherein the drive motor is provided by at least onepiezo-electromotor.
 39. The apparatus according to claim 37 wherein thecontrol unit and/or the imaging modality is electrically grounded. 40.The apparatus according to claim 37 wherein the control unit and/or theimaging modality is shielded from magnetic flux.
 41. The apparatusaccording to claim 40 wherein the shielding for magnetic flux is outsidethe imaging passage and is provided with ferrites.
 42. The apparatusaccording to claim 37 wherein the support or the body or the at leastone part of a body can be applied pressure and/or moved and/or rotatedand/or swiveled and/or pivoted independently about two axes.
 43. Theapparatus according to claim 42 wherein the support or the body or theat least one part of a body can be applied pressure and/or moved and/orrotated and/or swiveled and/or pivoted about a first horizontal axis ina horizontal plane and in a sagittal plane.
 44. The apparatus accordingto claim 37 comprising: means for fixing the body or the at least onepart of a body on the support; and at least portions of the support canbe moved relative to the means for fixing.
 45. The apparatus accordingto claim 37 wherein the drive of the support is in communication withthe imaging modality via the control unit, such that images are acquiredby the imaging modality simultaneously with the generation of thepassive movement.
 46. The apparatus according to claim 37 wherein theimaging modality is a magnetic resonance tomography.
 47. A magneticresonance tomograph comprising an apparatus for generating a passivemovement of the body or the at least one part of a body of the object orthe support according to claim
 37. 48. The apparatus of claim 37 whereinthe body or the at least one part of the body is a living object. 49.The apparatus of claim 37 wherein the passive movement comprisesapplying pressure and/or movement and/or swiveling and/or rotatingand/or pivoting to the body or the at least one part of a body or thesupport.
 50. The apparatus of claim 37 wherein the drive motor providesfor applying pressure and/or movement and/or rotating and/or swivelingand/or pivoting the support or the body or the at least one part of abody about at least one axis.
 51. The apparatus of claim 37 wherein thesupport or the body or the at least one part of a body can be appliedpressure and/or moved and/or rotated and/or swiveled and/or pivotedabout a first horizontal axis in a horizontal plane and in a sagittalplane.
 52. The apparatus according to claim 37 wherein the passivemovement produces or reproduces stress on the body or the at least onepart a body or the support.
 53. The apparatus according to claim 37wherein the passive movement imitates a physiological movement of thebody or the at least one part of the body.